fire safety valve free sample

One of the more recent developments in industrial tools to prevent fire is the introduction of fire safety valves. These valves are designed to prevent a fire from spreading if the fuel valve gets damaged or causes a leakage.

A valve is a device that adjusts, directs, or controls the flow of a fluid by opening, closing, or partially blocking various passageways. Valves are technically a type of fitting but are usually discussed separately. In an open valve, fluid flows from higher pressure to lower pressure. The simplest kind of valve is simply a freely hinged flap that drops to obstruct flow one way but is pushed open by fluid flowing the opposite way. This ancient valve is called a check valve, as it stops or "checks" the flow in one direction. Modern valves may regulate pressure or flow downstream and operate on sophisticated automation systems.

Valves have industrial applications for controlling processes, residential uses such managing water flow to dish and clothes washers and taps in the home. They are found in almost every industrial process, including mining, water and sewage processing, power generation, food manufacturing, processing of oil, gas and petroleum, chemical and plastic manufacturing, and many other fields.

Fire-safe valves are spring-loaded valves that are thermally actuated. In case of fire, they close automatically and stop the fuel flow. The fuel flow from the crankcase of the engine and the reserve oil supply gets hindered, thus minimizing the chances of leakage.

Spring-loaded valves help with preventing the flow of fuel such as oil, gas, petrol, and other combustibles, and are useful and effective against any damage. The benefits of using fire-safe valves in a system are the protection of human life, lower insurance rates, and the protection of equipment and the building.

It is because of these benefits that the use of these valves is highly recommended and appreciated. These days, many companies offer an extensive range of fire-safety valves to provide protection even in high temperature and high-pressure conditions.

A fire safety valve aims to keep ignitable fluids away from a flame. These valves close when exposed to heat, separating a flammable liquid from the heat source. They close in the midst of overheating of the pipeline, brought on by fire or similar events. The obligation to use fire safety valves is subject to any tenets, regulations, and laws concerning the unique methodology, plant, pipeline, or vessel.

Fire-safe ball valves use a combination of a floating ball, graphoil seals, and metal-to-metal seating to provide tight shut-off while preventing external stem leakage. In normal working conditions, the ball rests against two seats, ensuring bubble-tight closure. When the valve is exposed to a temperature above the limits the seats can withstand (for example, +450°F), the seats become deformed and are subject to extrusion. When the seats have been completely destroyed, the ball in the valve will come to rest firmly against the end cap, producing a metal-to-metal closing. Stem seals, which have high temperature-resistant properties, further restrict leakage in conjunction with a blow-out-proof anti-static stem, so that the flammable fluid stays separate from the heat source that may ignite it.

A fire-safe valve may also be made up of four main mechanisms: a spring pack, a trigger assembly, mounting hardware, and a fusible link. The components work in unison to close the valve should a fire be detected within a facility. The fusible link is the key part of the assembly. It keeps the valve open by maintaining tension on a spring pack through the trigger assembly. When a fire breaks out, the fusible link separates once it is heated to a certain high temperature, which releases the spring pack and allows it to close the valve.

A fire-safety valve with fusible links has a primary drop-tight seat, usually made of TFE, along with a second seat made of metal for isolation in a fire. The secondary seat also has graphite seals for further protection. This means that the shut-off valves can be paired with any quarter-turn ball valve, butterfly valve, or plug valve.

This article presents an understanding of fire safety valves. For more information on related products, consult our other guides or visit the Thomas Supplier Discovery Platform to locate potential sources of supply or view details on specific products.

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The primary purpose of a safety valve is to protect life, property and the environment. Safety valves are designed to open and release excess pressure from vessels or equipment and then close again.

The function of safety valves differs depending on the load or main type of the valve. The main types of safety valves are spring-loaded, weight-loaded and controlled safety valves.

Regardless of the type or load, safety valves are set to a specific set pressure at which the medium is discharged in a controlled manner, thus preventing overpressure of the equipment. In dependence of several parameters such as the contained medium, the set pressure is individual for each safety application.

In order to ensure that the maximum allowable accumulation pressure of any system or apparatus protected by a safety valve is never exceeded, careful consideration of the safety valve’s position in the system has to be made. As there is such a wide range of applications, there is no absolute rule as to where the valve should be positioned and therefore, every application needs to be treated separately.

A common steam application for a safety valve is to protect process equipment supplied from a pressure reducing station. Two possible arrangements are shown in Figure 9.3.3.

The safety valve can be fitted within the pressure reducing station itself, that is, before the downstream stop valve, as in Figure 9.3.3 (a), or further downstream, nearer the apparatus as in Figure 9.3.3 (b). Fitting the safety valve before the downstream stop valve has the following advantages:

• The safety valve can be tested in-line by shutting down the downstream stop valve without the chance of downstream apparatus being over pressurised, should the safety valve fail under test.

• When setting the PRV under no-load conditions, the operation of the safety valve can be observed, as this condition is most likely to cause ‘simmer’. If this should occur, the PRV pressure can be adjusted to below the safety valve reseat pressure.

Indeed, a separate safety valve may have to be fitted on the inlet to each downstream piece of apparatus, when the PRV supplies several such pieces of apparatus.

• If supplying one piece of apparatus, which has a MAWP pressure less than the PRV supply pressure, the apparatus must be fitted with a safety valve, preferably close-coupled to its steam inlet connection.

• If a PRV is supplying more than one apparatus and the MAWP of any item is less than the PRV supply pressure, either the PRV station must be fitted with a safety valve set at the lowest possible MAWP of the connected apparatus, or each item of affected apparatus must be fitted with a safety valve.

• The safety valve must be located so that the pressure cannot accumulate in the apparatus viaanother route, for example, from a separate steam line or a bypass line.

It could be argued that every installation deserves special consideration when it comes to safety, but the following applications and situations are a little unusual and worth considering:

• Fire - Any pressure vessel should be protected from overpressure in the event of fire. Although a safety valve mounted for operational protection may also offer protection under fire conditions,such cases require special consideration, which is beyond the scope of this text.

• Exothermic applications - These must be fitted with a safety valve close-coupled to the apparatus steam inlet or the body direct. No alternative applies.

• Safety valves used as warning devices - Sometimes, safety valves are fitted to systems as warning devices. They are not required to relieve fault loads but to warn of pressures increasing above normal working pressures for operational reasons only. In these instances, safety valves are set at the warning pressure and only need to be of minimum size. If there is any danger of systems fitted with such a safety valve exceeding their maximum allowable working pressure, they must be protected by additional safety valves in the usual way.

In order to illustrate the importance of the positioning of a safety valve, consider an automatic pump trap (see Block 14) used to remove condensate from a heating vessel. The automatic pump trap (APT), incorporates a mechanical type pump, which uses the motive force of steam to pump the condensate through the return system. The position of the safety valve will depend on the MAWP of the APT and its required motive inlet pressure.

This arrangement is suitable if the pump-trap motive pressure is less than 1.6 bar g (safety valve set pressure of 2 bar g less 0.3 bar blowdown and a 0.1 bar shut-off margin). Since the MAWP of both the APT and the vessel are greater than the safety valve set pressure, a single safety valve would provide suitable protection for the system.

Here, two separate PRV stations are used each with its own safety valve. If the APT internals failed and steam at 4 bar g passed through the APT and into the vessel, safety valve ‘A’ would relieve this pressure and protect the vessel. Safety valve ‘B’ would not lift as the pressure in the APT is still acceptable and below its set pressure.

It should be noted that safety valve ‘A’ is positioned on the downstream side of the temperature control valve; this is done for both safety and operational reasons:

Operation - There is less chance of safety valve ‘A’ simmering during operation in this position,as the pressure is typically lower after the control valve than before it.

Also, note that if the MAWP of the pump-trap were greater than the pressure upstream of PRV ‘A’, it would be permissible to omit safety valve ‘B’ from the system, but safety valve ‘A’ must be sized to take into account the total fault flow through PRV ‘B’ as well as through PRV ‘A’.

A pharmaceutical factory has twelve jacketed pans on the same production floor, all rated with the same MAWP. Where would the safety valve be positioned?

One solution would be to install a safety valve on the inlet to each pan (Figure 9.3.6). In this instance, each safety valve would have to be sized to pass the entire load, in case the PRV failed open whilst the other eleven pans were shut down.

If additional apparatus with a lower MAWP than the pans (for example, a shell and tube heat exchanger) were to be included in the system, it would be necessary to fit an additional safety valve. This safety valve would be set to an appropriate lower set pressure and sized to pass the fault flow through the temperature control valve (see Figure 9.3.8).

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NFPA 20 also requires a pressure relief valve on electric variable speed limiting controllers when the churn pressure is higher than the rating of the system components (NFPA 20 2013 4.18.1.3).

We try to avoid exceeding 175 psi in a system to begin with but will use high-pressure pipe and components for portions that are exceeded. NFPA 20 (A.4.7.7) hasn"t allowed the use of pressure relief valves to reduce pressure since 2003 for normal operation, but does permit pressure reducing valves (A.4.7.7.2).

A fire-safety shut-off valve, also known by thermal shut-off valve or simply afusible link valve, is a safety device designed to provide automatic valve shut-off in the event of a fire. Fire-safety valves of this type are designed for facilities that utilize flammable or toxic gases and chemicals in their production or for fuel systems of all types.

The fusible link is an FM and/or UL approved two-part linkage held together by a specialized heat-sensitive solder. These link(s) hold the fire safety valve open by keeping tension on a spring pack through a trigger assembly.

A fire safety shut-off valve is comprised of five main components – API 607 fire-safe valve, spring pack, mounting hardware, trigger assembly, and fusible link. The last four of these components work in unison to close the API 607 valve should a fire be detected within a facility.

The fusible link portion is the linchpin of the assembly and keeps the fire safety valve open by keeping tension on a spring pack through the trigger assembly. When a fire breaks out, the link separates when its rated temperature is met, releasing the spring pack and allowing it to close the valve.

The API 607 standard is a specification for the fire testing of quarter-turn valves. For fire-safety valve with fusible links, this means that the valves have a primary drop-tight seat, typically made of TFE, along with a secondary seat made of metal for isolation in a fire. The secondary seat is coupled with graphite seals for further protection. This means the top works of the shut-off valve can be paired with any quarter-turn API 607 fire safe valve – ball valve, butterfly valve, or plug valve.

Fusible link fire-safety valves are used in a variety of industries within an organization’s overall fire safety system for widespread fire protection. Most modern facilities have at diesel generators and day tanks that that requires this type of safety valve at a minimum. Other locations where flammable or toxic media are part of the production process, this valve type is placed at strategic locations throughout facilities including storage tanks, pumps, entryways into a building, and at key piping junctions. Entryways into buildings are especially key so that have employees, customers, and patients have as much time for notification and evacuation as possible.

A fire safety valve should be used as a safety precaution on any system that utilizes flammable or hazardous media. Designed to save lives and enable quick resumption of operations after a fire has been handled, fusible link assemblies are necessary for the safe daily operations of many commercial operations, plants, and manufacturing facilities. Many of these operations will find that insurance for their business is not available without a fire safety valve with fusible link.

BI-TORQ has been designing this type of assembly for over two decades. Let’s have a conversation about your fire safety needs and how our products can provide safety for your workers and operation. Contact us for more information on fire safety valves with fusible links, or to discuss any of our wide range of valve solutions.